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Explore our premium refractory solutions designed for high-stress zones in glass manufacturing facilities.
Modern glass manufacturing plants operate under some of the most extreme industrial environments on Earth. To melt silica sand and other raw components into high-quality glass, melting furnaces must maintain continuous operating temperatures exceeding 1500°C to 1600°C. Within these environments, molten glass acts as a highly corrosive liquid, dissolving ordinary materials and causing rapid structural degradation. The choice of refractory lining in these plants directly influences the longevity of the furnace, the thermal efficiency of the plant, and the purity of the produced glass. This is where Zirconia Refractory Bricks become indispensable.
Zirconia (Zirconium Dioxide, ZrO2) exhibits an exceptionally high melting point (approximately 2715°C), outstanding chemical inertness, and superior resistance to acidic and basic slag and molten glass. In glass manufacturing plants, zirconia-based refractories, including fused cast Alumina-Zirconia-Silica (AZS) and high-purity zircon bricks, are strategically deployed in areas facing the most severe thermal and chemical attacks. By creating a robust barrier against the corrosive flow of molten glass, these bricks prevent premature furnace failures and help glass manufacturers achieve furnace campaign lives of 10 to 15 years.
As molten glass flows through the furnace, it dissolves the refractory lining. If the lining material has low chemical resistance, it releases impurities into the glass melt, resulting in defects like "stones" (undissolved refractory particles), "cords" (glass with different refractive indexes), and "blisters" (gas bubbles). Zirconia refractories minimize these defects due to their extremely low solubility in molten glass, ensuring the production of defect-free, high-clarity glass products.
The global demand for zirconia refractories is experiencing steady growth, closely aligned with the expansion of high-tech glass applications. While traditional container glass and flat glass remain steady markets, the rapid rise of specialty glass sectors has heightened the performance requirements for furnace linings. Key drivers include:
Commercially, glass manufacturers are shifting away from frequent maintenance cycles toward extended furnace campaigns. Unscheduled shutdowns for hot repairs can cost plants millions of dollars in lost production. Consequently, purchasing premium zirconia refractories is viewed as a high-return investment that guarantees operational continuity and reduces the total cost of ownership over the furnace life cycle.
To understand the performance of zirconia refractories, it is necessary to examine their mineralogical structure and behavior under thermal stress. Pure zirconia undergoes a phase transition during heating and cooling. At room temperature, it has a monoclinic crystal structure. Upon heating past 1170°C, it transitions to a tetragonal structure, accompanied by a volumetric contraction of about 4% to 5%. During cooling, the reverse transition causes expansion, which can lead to cracking in pure zirconia bricks.
To prevent this, refractory engineers stabilize zirconia using oxides such as yttria (Y2O3), magnesia (MgO), or calcia (CaO), or combine it with alumina and silica to form Alumina-Zirconia-Silica (AZS) composites. In AZS refractories, the zirconia crystals are embedded in a glassy matrix, which absorbs the thermal expansion stresses. When molten glass contacts the brick surface, the silica-rich glass phase within the AZS brick forms a highly viscous boundary layer. This layer prevents further penetration of the molten glass into the brick structure, creating a self-protecting mechanism that limits corrosion rates.
At high temperatures, the glassy phase in some refractories can exude (squeeze out) to the surface, bringing impurities into contact with the molten glass. High-quality zirconia bricks are engineered with low glass phase exudation characteristics, making them highly stable in critical areas like the furnace crown and superstructure, where temperatures are at their highest.
Zirconia refractory bricks are strategically deployed in specific zones of the glass furnace where thermal and chemical stresses are concentrated:
1. The Furnace Throat: The throat connects the melting basin to the refining basin. All molten glass must pass through this narrow passage, creating high-velocity flow and severe mechanical erosion. The throat is also subjected to severe temperature gradients. Fused cast AZS blocks with high zirconia content (typically 41% ZrO2) are standard for this area to withstand the combined forces of chemical corrosion and physical wear.
2. The Melting Basin Sidewalls (Glass Line): The interface between the molten glass and the furnace atmosphere (the glass line) is the most vulnerable part of the basin. The continuous movement of the glass, combined with the presence of unreacted batch materials and corrosive gases, accelerates wear. Zirconia-based blocks are used along the glass line to prevent premature breaches.
3. The Feeder Channel and Forehearth: In the forehearth, the temperature of the molten glass is adjusted before forming. The refractories in this zone must be completely stable to avoid introducing defects just before the glass is shaped. High-purity zircon bricks are preferred for feeder channels due to their excellent thermal stability and low defect-generation potential.
4. Electrode Blocks: In furnaces that utilize electric boosting, electrodes are inserted directly through the refractory walls to pass current through the molten glass. The refractory blocks surrounding these electrodes experience high localized temperatures and electrical currents. Zirconia refractories, with their high electrical resistivity at elevated temperatures, prevent electrical shorting and localized wear around the electrodes.
The glass manufacturing industry is actively working to reduce its carbon footprint, leading to changes in furnace design and operation that impact refractory requirements:
Oxy-Fuel Firing: Replacing combustion air with pure oxygen improves thermal efficiency and reduces nitrogen oxide (NOx) emissions. However, oxy-fuel combustion increases the concentration of water vapor and volatile alkali species in the furnace atmosphere. This aggressive atmosphere accelerates the corrosion of traditional silica crowns. As a result, glass plants are increasingly adopting zirconia-based and chrome-zirconia refractories in the superstructure to resist alkali vapor attack.
All-Electric Melting: To eliminate direct carbon emissions, some plants are transitioning to all-electric melting. These furnaces rely entirely on electrodes to melt the batch. The absence of gas burners alters the temperature distribution within the furnace, concentrating heat in the lower part of the basin. This configuration requires refractories with high thermal resistivity and excellent resistance to hot-spot corrosion, driving the adoption of high-zirconia linings.
Circular Economy and Recycling: Refractory manufacturers are developing technologies to recycle spent zirconia bricks. After a furnace campaign, used AZS and zircon blocks can be crushed, purified, and reused as raw materials for new refractories, reducing raw material consumption and minimizing waste.
Zhengzhou SK Refractory Co., Ltd. (SK) located in Xinmi, Zhengzhou China, For over twenty years, SK Refractories dedicated to delivering high-performance, reliable solutions that redefine durability and efficiency for our clients worldwide. Founded on the principles of innovation, quality, and sustainability, serving key sectors including steelmaking, cement production, non-ferrous metallurgy, glass manufacturing, and petrochemical processing.
SK Refractories’ quality is embedded in every aspect of our operations, from raw material sourcing to production and delivery. We partner with trusted suppliers to secure premium-grade raw materials, leveraging advanced manufacturing processes—such as automated pressing, and controlled sintering—to ensure consistency and reliability. Our quality management system is certified to ISO 9001, reflecting our dedication to maintaining the highest standards of excellence.
SK Refractories main refractory products for industry furance are, zircon bricks, corundum brick, mullite bricks sillimanite bricks, silica bricks, magnesia bricks, low porosity firecaly blocks, insulation bricks and etc. SK Refractories has the annual production capacity of 20000+ tons, With scientific managment, advanced technology and equipment, and strict quality control process, SK Refractories can esure the high quality of the refractory bricks for industry furnace.
SK Refractories is well known in domestic markets and abroad for the quality of refractory bricks. The refractory materials produced by SK Refractories have been exported to more than 35 countries such as America, Spain, Germany, Italy, Brazil, Belgium, India, Japan, Korea, etc. The main products include Silica Brick, low porosity firecaly blocks, Sillimanite Brick, Corundum Brick, Zircon Brick, Mullite Brick, Insulating Bricks, refractory castables and refractory mortar of related materials.
Our obligation is to supply high quality refractory materials and service to achieve long lifetime of high temperature furnaces. SK Refractories will always improve himslef to provide better refractory products and service to the customers all over the world.
Explore our complete range of high-temperature refractory solutions for glass manufacturing and industrial kilns.
We sincerely welcome both new and existing international customers to cooperate with us in a friendly manner and work together to create a bright future!